The present invention relates to a notch alignment apparatus for aligning the notches of target objects, such as semiconductor wafers, contained in a container and arrayed in a facing state, and an adjustment jig for the notch alignment apparatus.
In manufacturing semiconductor devices, a container, which is also referred to as a carrier or cassette, is used for containing a plurality of target objects, i.e., semiconductor wafers, in a facing state when the wafers are transferred among processing steps. Semiconductor wafers are provided with orientation flats or notches, i.e., cut-out portions, respectively, at their peripheral edges to easily judge and align their crystal orientations.
Jpn. Pat. Appln. KOKAI Publication Nos. 6-345028 discloses a notch alignment apparatus for aligning the notches n of a plurality of semiconductor wafers W, contained in a container C and arrayed in a facing state. The apparatus have an alignment unit. The alignment unit has a driving shaft for coming into contact with the peripheral edges of the wafers from below to drive the wafers to rotate all together; a plurality of idle pulleys 20 independent of each other and arranged on one side of the driving shaft, for coming into contact with the peripheral edges of the wafers from below; and a stopper 30 arranged on the other side of the driving shaft, for stopping rotation of the wafers by means of contact with the peripheral edges of the wafers.
In this apparatus, each wafer W is essentially supported by the driving shaft and the corresponding idle pulley 20 while the wafer is rotated by the driving shaft. When the notch n of the wafer engages with the driving shaft and the wafer leans the peripheral edge of the wafer comes into contact with the stopper 30, thereby causing the wafer to stop its rotation. In this way, the notches of the wafers are aligned in the axial direction of the driving shaft.
Jpn. Pat. Appln. KOKAI Publication No. 7-235587 discloses a notch alignment apparatus for aligning the notches 2 of a plurality of semiconductor wafers 3, contained in a container 4 and arrayed in a facing state. The apparatus has an alignment unit 7 which is capable of moving up and down so that it can advance into the container through the bottom opening of the containers. The alignment unit has a driving shaft 11 (12) for coming into contact with the peripheral edges of the wafers from below to drive the wafers to rotate all together; a plurality of idle pulleys 43 independent of each other and arranged on one said of the driving shaft, for coming into contact with the peripheral edges of the wafers from below; and a stopper 28 arranged on the other side of the driving shaft, for stopping rotation of the wafers by means of contact with the peripheral edges of the wafers.
In this apparatus each wafer W is essentially supported by the driving shaft 11 and the corresponding idle pulley 43 while the wafer is rotated by the driving shaft. When the notch 2 of the wafer engages with the driving shaft and the wafer inclines, the peripheral edge of the wafer comes into contact with the stopper 28, thereby causing the wafer to stop its rotation. In this way, the notches of the wafers are aligned in the axial direction of the driving shaft.
In this type apparatus, however, alignment of the notches can not be correctly performed on occasion, because slip is caused between the driving shaft and the wafers, or the notches pass over the driving shaft, depending on the state of the wafers, for example, a state brought about after film formation. More specifically, the driving shaft is generally coated with a fluoro-resin to enhance its physical and chemical withstand capability, which in return results in a low frictional resistance. On the other hand, the peripheral edges of the wafers also have a low friction resistance, and much less especially after a film formation process, depending on the film material. Further, each notch generally has an opening width smaller than the diameter of the driving shaft. In addition, after a film formation process, the size of each notch becomes slightly smaller. As a result, the notches become apt to pass over the driving shaft. In this respect, the driving shaft may be coated with silicone rubber to improve the rotational driving capability of the driving shaft, but the silicone rubber is easily worn out.
On the other hand, such a notch alignment apparatus is known that has an optical sensor for confirming alignment of the notches. See U.S. Pat. No. 5,533,243. The sensor senses alignment of the notches in a state where the wafers are supported by and in a container after a notch alignment operation is finished and an alignment unit is moved down. By using the optical sensor, it is possible to raise an alarm or to repeat the notch alignment operation, if the notch alignment has not been correctly performed.
However, in the apparatus of this type, the notches and the optical axis of the optical sensor are not lined up on occasion due to a deformation or dimensional error of the container, thereby bringing about a sensing error. Further, the sensing accuracy of the optical sensor depends on its arranged state. Since the notch alignment apparatus is periodically disassembled, cleaned, and reassembled, it becomes more important to assemble it with high precision.